1. Field of the Invention
The present invention relates generally to a system and a method for providing a presence service, and more particularly to a system and a method for directly requesting and receiving presence information from a presence source.
2. Description of the Related Art
In general, a presence service refers to a service for properly notifying a series of objects interested in a certain subject of concern, such as a user or a group, of information regarding a current state of communication of the subject, through a series of devices. Based on published state information about a subject of concern, the series of objects can understand a current situation of communication about the subject of concern, and can also select a communication means, which is optimized, i.e. has the highest probability of success, at a desired time so as to try to make contact with the subject of concern. At this time, a user, which is a subject to be observed, refers to a presentity, communication state about the user refers to presence information, and a user who receives the information refers to a watcher.
With reference to FIG. 1, a simplified architecture of a presence service is shown. A subject of concern in the presence service refers to a presentity, and presence sources 120 collect information regarding the presentity, i.e. presence information, and publishes the information to a presence server 110. The presence server 110 composes pieces of presence information, generates aggregated presence information about the presentity, and notifies objects interested in the presentity, i.e. watchers 100, of the aggregated presence information.
A signal flow between such functional entities of the presence server will be described with reference to FIG. 2.
Whenever presence information of a presentity is changed, the presence source 120 publishes changed presence information to the presence server 110 by using SIP (Session Initiation Protocol) PUBLISH, which is defined in “RFC3903 “SIP Extension for Event State Publication””, through a SIP/IP (Session Initiation Protocol/Internet Protocol) core 140. Then, the presence server 110 composes many pieces of presence information published from the presence source 120 into one piece of presence information so as to maintain the latest presence information about the presentity. Such a step where the presence source 120 publishes changed presence information to the presence server 110 by using SIP PUBLISH according to the change of presence information may be illustrated in steps 200, 203, 212, and 215.
Meanwhile, in a case where a watcher 100 requests presence information about a corresponding presentity from the presence server 110 according to presence event package defined in “RFC3856 “A Presence Event Package for the SIP””, the presence server 110 notifies the watcher 100 of the requested presence information by using SIP NOTIFY through SIP/IP core 140. Also, a step of notifying, by the presence server 110, the watcher 100 of presence information about a presentity by using SIP NOTIFY may be illustrated in steps 208 to 211.
Also, in a case where the presence source 120 publishes changed presence information to the presence server 110 by using SIP PUBLISH according to change of presence information in steps 212 to 215, the presence server 110 notifies the watcher 100 of the presence information by using SIP NOTIFY through steps 216 to 219. Particularly, the presence server 110 notifies the watcher 100 of the latest presence information by using SIP NOTIFY whenever presence information about a corresponding presentity is changed.
In the case of FIG. 2, the presence server 110 collects presence information about the presentity only when the presence source 120 publishes the presence information thereto. Particularly, collection of presence information about a presentity in the presence server 110 is entirely up to voluntary publication performed by the presence source 120.
In order to complement this, a method for allowing the presence server 110 to directly request information publication from the presence source 120 by using SIP REFER defined in “RFC3515 “The SIP REFER Method””.
As such, the flow of a signal for allowing the presence server 110 to directly request the presence source 120 to publish presence information will be described with reference to FIG. 3. Firstly, a step where the presence source 120 publishes changed presence information to the presence server 110 by the can be illustrated in steps 300 to 303.
Then, when the watcher 100 requests presence information about a corresponding presentity from the presence server 110 by using SIP SUBSCRIBE, the presence server 110 notifies the watcher 100 of the presence information about the presentity according to the request. A step of requesting presence information of a presentity and a step of publishing presence information according to the request may be illustrated in steps 304 to 311.
Meanwhile, the presence server 110 requests presence information from the presence source 120 by using SIP REFER. According to the request, the presence source 120 publishes the requested presence information to the presence server 110 by using SIP PUBLISH. Accordingly, the presence server 110 updates presence information about the corresponding presentity and notifies the watcher 100 of the presence information by using SIP NOTIFY. As such, a step where the presence server 110 directly requests presence information about a presentity from the presence source 120, and after receiving presence information, notifies the watcher 100 of the presence information will be described in the same manner as steps 312 to 323.
As described above, in the prior art, in order to improve a problem in that collection of presence information about a presentity in the presence server 110 has no choice but to be entirely up to voluntary publication performed by the presence source 120, such a manner that the presence server 110 directly requests presence information about a presentity from the presence source 120, receives the presence information, and notifies the watcher 100 of the presence information has been developed.
However, the prior art discloses only the fact that the presence server 110 directly requests presence information about a presentity from presence source 120, receives presence information, and notifies the watcher of the presence information as shown in FIG. 3. But, the prior art does not disclose how the presence server 110 identifies a specific presence source and routes SIP REFER requesting presence information about a corresponding presentity to a corresponding presence source 120 through the SIP/IP core 140.
Also, in the above described method as shown in FIG. 3, only the fact that the presence server 110 requests presence information about a corresponding presentity from the presence source is described, and how the presence source 120 publishes the corresponding presence information is not described.
Also, in the method as shown in FIG. 3, where presence server 110 requests presence information from the presence source 120 is not described.